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Retroperitoneal and pelvic lymph node imaging

Article Abstract:

The lymphatic system provides a route for metastatic spread that is utilized by the majority of malignant tumors. Most cancers, if not treated, spread first to local lymph nodes, then to further lymph nodes, and then invade distant organs of the body. Therefore, the staging of cancer usually involves the determination of lymph node involvement. Indeed, the ''N'' in the TNM staging system used for most cancers stands for nodal involvement. (T indicates the stage of the primary tumor, and M indicates metastasis.) Each cancer and each anatomical region of the body has its own special propensities. The author provides a review of the use of imaging techniques in the examination of pelvic and retroperitoneal lymph nodes (which do not include nodes that lie within the abdominal cavity itself). These lymph nodes group are at primary sites of lymphatic drainage. Therefore, they are very likely to be invaded by cancer cells from the prostate, testes, ovaries, uterus and cervix, kidneys, and bladder. Clearly, the evaluation of these lymph nodes is a critical aspect of the evaluation and staging of a host of relatively common malignant tumors. Lymphography uses contrast material to opacify lymph nodes and render them more visible on X-ray. The technique is old, having been introduced in the 1950s, but is still highly regarded for producing an excellent image of the lymphatic system. That lymphography has been replaced by computed tomography (CT) is probably more of an indication of the technical skill required for lymphography, rather than the superiority of CT. The modern techniques of CT scanning, ultrasound, and magnetic resonance imaging rely on the size of lymph nodes for the detection of metastatic disease. CT and MRI have the advantage of not relying on operator skill to any great degree and imaging all lymph nodes simultaneously. It is hoped that the usefulness of MRI improves as new contrast agents are developed. A still largely unexplored area, which may provide useful insights even prior to the enlargement of lymph nodes, is that of scintigraphy. It may be possible to use specific radioactive tracers, perhaps monoclonal antibodies specific for tumor cells, to construct an image in which lymph nodes actually contain the seeds of a new generation of cancerous cells. (Consumer Summary produced by Reliance Medical Information, Inc.)

The non-Hodgkin lymphomas: practical concepts for the diagnostic radiologist

Article Abstract:

Traditionally, malignant lymphoma (cancer of the lymph nodes) has been categorized as either Hodgkin's (HD) or non-Hodgkin's (NHLs). Information about NHLs has increased in recent years, allowing for better classification, diagnosis, and treatment of this heterogenous group of lymph node cancers. Information useful to imaging and diagnosing NHLs is presented. NHLs can occur at any age, are of unknown cause, and are more common in people with immune deficiencies such as AIDS (acquired immunodeficiency syndrome). Traditional diagnosis of the disease has been based on the Rappaport classification, which uses the appearance of tissue sample under a microscope to diagnose and differentiate NHLs. A newer classification has been developed, known as the Working Formulation of NHL. It differentiates tumors on the basis of whether they are diffuse (spread out) or follicular (distinct), whether they are small or large, and by grades. This new classification helps decide treatment approach and prognosis. Anatomic staging is done using the Ann Arbor classification scheme developed for HD. However, it fails to take into account tumor bulk, which is more important in NHLs. Anatomic extent of disease at diagnosis is less important in determining outcome of NHLs than of HD. NHLs are also frequently involved in other areas besides the lymph nodes, unlike HD. Patients with low-grade NHLs often go into remission without treatment, and treatment at this stage has little effect on outcome and may not be necessary. Diagnostic imaging of NHLs is accomplished using X-rays and computed tomography (CT). Magnetic resonance (MR) imaging may also be useful, since it can image bone marrow, which is often involved in NHLs. The use of imaging in characterizing and managing NHLs varies by area of the body. Use of CT information from the chest area is not well studied. It can be helpful in diagnosing, staging and treating NHL infiltration of areas in the pelvis and the abdomen as well as other sites outside the lymphatic system. (Consumer Summary produced by Reliance Medical Information, Inc.)

Lymphomas are tumors of the lymphatic system. Malignant lymphomas are generally broken into two major classes, Hodgkin's lymphoma and the diverse groups of conditions collectively called non-Hodgkin's lymphoma. A full 85 percent of patients with Hodgkin's lymphoma will have lymph nodes of the chest involved at the time of their initial presentation; about half the non-Hodgkin's lymphoma patients will have chest involvement. Newly diagnosed patients should have chest CT scans, which will provide information that is useful in designing the treatment protocol. Unfortunately, the potential advantages of magnetic resonance imaging in this regard have not been fully evaluated. For the examination of lymph nodes in the pelvis and behind the peritoneal cavity, the most accurate method seems to be lymphography, which enhances the contrast of the lymph nodes. However, this technique is highly specialized and, at present, requires expertise that is not available at all medical centers. Therefore, computed tomography is the most practical method for examining these sites, as well. Unfortunately, computed tomography is not particularly effective in the examination of lymph nodes below the diaphragm, in the mesentery, the celiac axis, an related sites. Furthermore, no method of imaging is effective in the detection of tumor within the spleen or the liver. From 30 to 40 percent of lymphoma patients have spleen involvement. It is hoped, however, that the development of contrast techniques for magnetic resonance imaging may improve the detection of small tumors in the spleen. It may also become possible to detect small tumors in the spleen using reflected ultrasound, but these techniques are in early stages of development. (Consumer Summary produced by Reliance Medical Information, Inc.)